Is there any difference between Sunnah, mustahabb and nafil?

Question

What is the difference between Sunnah and Nafel? and Sunnah and Musthab?

Answer

Praise be to Allaah.

The
majority of scholars of Usool al-Fiqh say that there is no difference
between Sunnah, mustahabb, tatawwu’ (voluntary actions) and nafil. But
the Hanafis say something different. They regard mandoob (recommended)
as being of the same status as nafil, and they differentiate between
Sunnah and nafil, regarding Sunnah as being higher in status.